Radiation furnace



June 13, 1961 A. v. GROSSE RADIATION FURNACE 4 Sheets-Sheet 1 Original Filed July 25, 1957 INVENTOR.

BY W

June 13, 1961 A. v. GROSSE 2,988,022

RADIATION FURNACE Original Filed July 25, 1957 4 hee -Sh et 2 INVENTOR /4e/J 770 690555 ATTORNEY June 13, 1961 A. v. GROSSE RADIATION FURNACE 4 Sheets-Sheet 3 Original Filed July 25, 1957 wmwww INVEN'I' OR.

OXYGEN Rn TE -A usapaeMm/wz ArsrP June 13, 1961 A. v. GROSSE RADIATION FURNACE 4 Sheets-Sheet 4 Original Filed July 25, 1957 'Tlcri INVENTOR.

2,988,022 Patented June 13, 1961 4 Claims. (31. 110- 1 This invention relates to the radiation of intense radiant heat energy from a wide area at a high temperature by the rapid burning of aluminum.

This energy can be usefully used for subjecting various types of material to intense radiant heat. This testing is desirable not only to determine the characteristics of various materials, but also to develop materials that are resistant to the intense radiant energy emitted by nuclear explosions.

The main object of the invention is to provide radiant heat having a high radiant flux density over an extended area.

Another object of the invention is to produce, by the release of chemical energy, heat having a high radiant flux density over an extended area.

Another object of the invention is to produce from the combustion of aluminum a high radiant heat fiux density over an extended area.

A further object of the invention is to provide a combustion apparatus for burning aluminum within a confined chamber and for emitting radiant heat energy over an area for sustained periods of time.

These and other objects of the invention will become more apparent upon consideration of the following description taken together with the accompanying drawings, in which;

FIG. 1 is a vertical sectional view of a preferred embodiment of the apparatus for providing intense radiant energy according to this invention;

FIG. 2 is a perspective view of the completely watercooled apparatus illustrated in FIG. 1 for emitting radiant energy according to this invention;

FIG. 3 is a perspective view of the lower part of the apparatus of FIG. 2 with upper part removed;

FIG. 4 is a chart of the stoichiometric rate of feed of aluminum corresponding to the variation of the rate of feed of oxygen;

FIG. 5 is a section illustrating the components of this invention;

FIG. 6 is a section of modified shutter part for the apparatus of FIG. 2;

FIG. 7 illustrates a fragmentary view of the furnace supplied with aluminum in rod form; and

FIG. 8 illustrates another embodiment of the combustion apparatus.

In accordance with this invention, aluminum is burned within a confined space of a combustion apparatus having a refractory wall for supporting the molten aluminum oxide resulting from the burning of the aluminum discshaped pool floating on the surface of the aluminum oxide. The confined space of the combustion apparatus is provided with means for emitting the intense radiation produced by the burning of the aluminum for various purposes later herein described.

In FIG. 1, a preferred form of the combustion apparatus is shown and illustrates the molten aluminum oxide pool formed by the burning and the molten aluminum disc-shaped pool formed from the aluminum fed into the combustion apparatus. The combustion apparatus comprises a casing 24 for supporting a refractory vessel '29, a top 23 having an opening for permitting the emission of radiant energy and having means for supplying oxygen;

and a shutter for covering the emission opening to close the confined space.

The casing 24 comprises a bottom 24a and side walls 24b, 0, d and e, and a top panel 24f having a receptacle 24g for supporting the refractory receptacle lining 29. The walls 24b, c, d and a fourth wall not shown and the bottom 24a are spaced from the receptacle 24g to provide a chamber 24h for circulating cooling water around the lining 29 to maintain the combustion apparatus at a desired temperature and condition of operation. The casing 24 has fittings 28, 41, 42 for circulating a cooling medium or water through the chamber in the casing 24.

In the preferred embodiment, the walls and panels of the casing 24 and the receptacle 24g may be made of sheet steel and have a depth of 6 inches and a length of 14 inches along each side. The receptacle 24g has generally cylindrically shaped sides which are tapered to permit the positioning of the receptacle 29, and has a bottom 24 spaced from the bottom 24a of the casing. The receptacle has a diameter of approximately 12 inches and a depth of approximately 5 inches, so that ample space is provided around the sides and the bottom of the receptacle 24g to maintain the furnace at the desired temperature and operating conditions.

The receptacle 29 may be made of a ceramic mix containing a coarse aluminum oxide, a fine aluminum oxide and a bentonite. More specifically, these ingredients may be mixed in dry proportion as follows: 600 parts by Weight of coarse aluminum oxide, 200 parts by weight of fine aluminum oxide and 24 parts by weight of bentonite. After mixing, water is gradually added until the mix attains the proper consistency. In the proper consistency, a handful of wetted mixture will hold its shape.

The top panel 24 of the casing 24 has an opening 30. The receptacle 29 is formed by shaping the wet material in the receptacle 24g until the walls 29a and 29b are from to /2 inch thick. The wet receptacle 29 in its proper shape is removed from the receptacle 24g and is fired to form the solid heat resistant receptacle ready for use. The walls 29a may be straight or tapered. A slight taper is desired to facilitate the removal of the receptacle from the casing 24. In a preferred form, the receptacle 29 may have an inside diameter of 12 inches and an inside depth of 5 inches to provide adequate space for the combustion process.

The top '25 of the combustion apparatus comprises upper and lower panels 25a and 25b separated by side walls 250, d, e and a wall not shown, to form a confined cooling chamber within the top. The upper and lower panels have an opening through this with an annular ring 34 secured to the upper and lower walls and defining the walls of the passage through the top. The ring 34 has a plurality of circumferentially spaced openings preferably twenty in number, and connected to a circumferentially extending passage around the annular member 34 by means of ducts 34b, and these are at a vertical angle to direct the oxygen upwardly, away from the receptacle 29.

The passage is connected to a suitable supply of oxygen by means of conduits 35 extending through the opposite walls 250 and 25e. The passage may be formed by a tubing 34c welded or brazed to the outer annular surface of the ring 34. Thus, the oxygen supplied by the conduits 35 is fed circumferentially around the annular ring 34 to provide a uniform feed of oxygen to the combustion apparatus.

The cover 25 is coextensive with the casing 24 and has a thickness or depth of approximately 1 inch. Fittings 33 and 43 are mounted in the side walls 25e and fitting 44 is mounted in the side wall 250 to circulate a cooling medium such as water through the top 25 to maintain the top at the desired operating temperature.

The radiant energy opening in the top 25 in the preferred embodiment is approximately 6 inches in diameter to provide ample area for the emission of the radiation from the combustion apparatus.

The lower or inner panel 25b of the top is exposed to the intense heat of the combustion process and the water maintains the temperature of this panel well within the operating limits. On the top panel 25a, parallel guides 37 are provided on opposite sides of the emission opening for guiding and positioning the movable shutter 26 which covers the emission opening. The cover 26 comprises upper and lower panels 26a and 26b spaced by side walls 26c, d, e and f, to form a hollow chamber 26g for circulating a cooling medium through the shutter. The upper and lower panels 26a and 26b have openings of substantially the same diameter as the emission opening in the top 25 and have an annular ring 39 Welded or brazed to the upper and lower panels to form a liquidtight seal to retain the cooling medium within the shutter. Fittings 38 are provided connected to the cooling chamber within the shutter for retaining the shutter at the proper operating conditions, either when the emission openings of the shutter and top are aligned or when the opaque portion of the shutter covers the emission opening. A handle 61 is provided for adjusting the position of the shutter depending upon the operative steps to be performed.

The shutter 26 may be made of sheet steel and has a width of approximately 8 inches, a length of approximately 14 inches, a depth of approximately 1 inch. Guides 40a and 40b are provided extending normal to the rails 37 for positioning the quartz window 40 over the emission passage. The quartz window forms a means for confining the thermal heat of the combustion reaction within the confined chamber and permitting the passage of radiant energy emitted by the combustion reaction. This radiant energy is extremely intense and may be used for various purposes such as testing materials. The quartz window is preferably 6 inches long along each edge and has a thickness of approximately inch. On Opposite sides of the emission openings, passages 46 and 47 are provided extending through the top 25 from the upper panel 25a to the lower panel 25b to permit the supply of aluminum, preferably in a rod or pellet form.

The orifices 34a direct the oxygen supply thereto upwardly towards the sight glass to clear the furnace of the powdered molten aluminum oxide formed from the combustion of aluminum. The sight glass is maintained cool by the impingement of the oxygen thereon and from the cooling medium circulating through the shutter 26. In the operation of the radiation furnace combustion apparatus, the cooling system is rendered operative by filling chambers of the shutter top and casing with the cooling medium or water by means of the fittings secured thereto. During the operation of the furnace, the circulation of the cooling water through the top and casing is discontinued. However, the flow of cooling water is maintained through the shutter 26.

The combustion process is initiated by placing an ig niter in the receptacle 29 through the emission passage 31. The igniter is composed of aluminum foil, aluminum powder with a mesh of about 200 or finer, and aluminum shavings. An igniter may be formed by wrapping a mixture of aluminum shavings and powder in a piece of aluminum foil. In one embodiment, a mixture of 25 grams of aluminum shavings and 50 grams of aluminum powder of 200 mesh or finer may be wrapped in a piece of aluminum foil to form a package around the mixture of shavings and powder of about 4 inches thick. The combustion reaction may be initiated by dropping a lighted match through the emission passage 31 on to the igniter and closing the shutter over the passage 31 to retain the heat within the combustion apparatus but leaving a slight opening; for observing the progress of initiating the combustion process, with the oxygen flowing into the combustion apparatus and a match igniting the aluminum igniter. An aluminum rod is inserted through the opening 46. The aluminum foil is punctured so that the match impinges upon the mixture of shavings and foil to ignite the powder, which in turn quickly ignites the shavings, causing the aluminum foil to melt and then burn. The heat of the burning aluminum foil melts the end of the aluminum rod to merge with the molten foil to form a pool of molten aluminum on the bottom of the refractory receptacle 29. The aluminum continues to burn, increasing in intensity as the heat of the combustion apparatus is raised. The aluminum oxide is formed as drops in a molten mist which condense along the walls of the receptacle 29 and the top 25, to collect in the bottom of the receptacle 29 as a molten pool of aluminum oxide.

As the combustion process proceeds, the aluminum rod is continually fed into the furnace to sustain the supply of molten aluminum, and the amount of aluminum oxide increases to enlarge the pool in the receptacle 29. The circulation of the cooling water is resumed through the top 25 and the casing 24 to maintain the walls of the combustion apparatus at the desired operating condition. The molten aluminum oxide is cooled along the walls of the receptacle 29 to further line the receptacle 29 with a solid refractory material. A large portion of the aluminum oxide remains in the molten state forming a liquid surface upon which the molten aluminum sets.

The molten pool forms a fluid plastic surface upon which the molten aluminum coalesces into a wafer-shaped globule 50 or disc-shaped pool with a generally flat convex surface 52 referred to as a skating sun. The heat from the combustion boils the aluminum in the globules to form a layer of vaporous aluminum over the surface of the globules. The vapor combines with the oxygen to burn in the zone 51. With the rapid burning of the aluminum, the vapor forms in a thin layer over the surface. The oxygen is supplied uniformly over the surface so that a brilliant disc-shaped flame is formed that may burn at a temperature of 3500 C. emitting large quantities of heat.

This reaction is continued with a continuous feed of aluminum and oxygen to produce skating suns of burning aluminum. The combustion product, molten aluminum oxide, accumulates in the bottom of the furnace 11, and the one or more skating suns or pools as previously described on the upper surface of the combustion product produce the radiant heat energy mentioned above. This radiant heat energy is observed, emitted and extracted from the furnace through the emission passage 31 and the sight glass apparatus 41.

At the higher rates of combustion of the aluminum sun or suns in the furnace 11, a smoke issues from the combustion reaction filling the chamber above the burning material. This smoke would interfere with the emission of radiant energy save for the sight aperture and the downward draft of introduced oxygen.

In a more specific description of the initiation of the combustion process and the operation of the furnace, the cooling water is supplied to the top and casing to fill the chambers with the cooling water. The flow of the water is discontinued in the top and casing, but the flow in the shutter is maintained as described above.

The above described igniter is placed in the bottom of the receptacle 29 through the emission passage 31 with the igniter setting flat on the bottom of the receptacle 29. The oxygen supply is set at the desired pressure, which is 30 pounds per square inch. The passage 31 is closed by the shutter 26 and oxygen is momentarily supplied to the combustion apparatus to clear the confined chamber of air. The supply of oxygen is discontinued and a lighted match or other suitable ignition means is dropped on the igniter. The passage 31 is then covered by the opaque portion of the shutter, except for a slight crack for observation purposes.

The oxygen is then supplied at a rate of 100 liters per minute and an aluminum rod is inserted through the opening 46 and the aluminum foil is punctured. The ignition means is then brought into contact with the aluminum powder and shavings within the igniter which initiates the burning of the aluminum. The foil of the igniter melts to form a disc shaped pool on the bottom of the receptacle 29. The heat of the burning of the molten aluminum melts the end of the aluminum rod to increase the size of the disc shaped pool.

As the aluminum burns, the aluminum rod is melted and the size of the pool gradually increases. When the pool increases to the diameter of approximately 4 inches, the circulation of the cooling water to the top and casing is resumed. The rate of oxygen fed is reduced to 80 liters per minute. The aluminum rod is fed continuously into the combustion apparatus until the diameter of the pool is approximately equal to the inside diameter of the receptacle 29. The rate of oxygen fed is then reduced to 50 liters per minute.

The temperature of the furnace has increased and the aluminum oxide pool is formed on the bottom of the receptacle with the pool floating thereon. The aluminum is vaporizing from the molten aluminum pool at a very rapid rate and the intensity of burning is very high, to produce high temperatures and emit large quantities of radiant energy.

With the furnace burning vigorously and emitting large quantities of high temperature radiant energy, it is in condition for testing purposes. A quartz plate may be positioned in an opening over the shutter to permit the emission of the intense radiant energy from outside of the furnace. Due to the high rate of emission of radiant energy and the temperature of the furnace, the quartz plate is aifected by the heat after a period of one minute. The quartz plate will be melted or cracked under the intense heat. Thus, the shutter must be shifted by the handle 61 from time to time to permit the quartz plate to cool or be replaced by another one, so that the operation may be continued.

When the receptacle 29 becomes filled with aluminum oxide, the oxygen is cut off and the receptacle 29 removed and the aluminum oxide contained therein dropped out. This is accomplished by removing the top 25 and inserting the casing 24 which permits the receptacle 29 to fall out of the casing.

Various means may be used for feeding the aluminum to the furnace. The aluminum may be fed in the form of rods hand operated or may be fed in the form of a wire from an automatic wire feed device. The aluminum rods may have diameters of A, to /2 inch and the aluminum wire may be of a suitable diameter such as of an inch.

With a constant supply of oxygen, the size of the pool will be determined by the rate of feed of the aluminum. The aluminum may be fed to increase the pool to large size and then the feed may be discontinued to permit the pool to slowly shrink in size. However, in most test purposes, it is desirable to maintain the pool at a constant size or diameter. Therefore, the aluminum should be fed in approximately stoichiometric proportions in the feed to the oxygen from the ports 34b. Allowance for leakage of oxygen from the combustion apparatus should be made.

In the wire feed device, aluminum wire of suitable diameter is wound on a spool. A drive mechanism draws the wire off the spool and delivers it to the furnace at a constant rate. This rate of feed is adjustable and may be regulated so that the aluminum wire maintains the pool at a constant diameter size. In using the wire-feed device to maintain the pool at a constant diameter size, it is necessary to feed the aluminum at a rate adjusted to by feeding the aluminum and oxygen at stoichiometric rates. As this assumes that all of the oxygen fed into furnace 23 is consumed in the combustion, slight adjustments may be necessary, as some oxygen may escape either through the feed hole 46 or a vent hole 47 provided in the top 25 for release of smoke produced in the combustion. FIG. 4 illustrates the stoichiometric ratio between the feed rates of aluminum and oxygen in grams per minute of aluminum and liters per minute of oxygen at standard temperature pressure. The oxygen is supplied from a tank of compressed oxygen through an automatic pressure regulator at a pressure of about 30 pounds per square inch.

Continuous operation by feeding aluminum rods may also be carried on to maintain the pool at a constant diameter by reference to the chart of FIG. 4 employing a knowledge of the weights per foot in grams of the feed rod. The following is a table of the weight per foot in grams of aluminum wire and three standard size aluminum rods.

Table 1 Diameter, inches: Grams per foot A 27 60 The intensity of the radiation is a function of the distance between the aluminum pool and the sight glass. As an average, a radiation of ten calories per square centimeter per second can be obtained at a distance of about five inches. The production of aluminum oxide by the combustion raises the level of the surface of the pool in the furnace and as the surface is thus moved toward the sight glass 40, the intensity of radiation is increased. The radiation may also be increased and decreased by variations in the oxygen rate with an increase in oxygen intensifying the radiation.

The radiation intensity may be measured by a spot calorimeter consisting of a copper square of substantial thickness held in and insulated from a copper frame and containing a thermometer which records temperature rise of the square from the absorption of radiation in a blackened face of the square. The radiant-flux density is calculated from the temperature data and the known mass of the copper square. The following is a table of radiation densities obtained from the operation of the furnace and calculated on the above described calorimeter.

Table II Radiant-flux density cal/cm. sec.

Distance between pool and sight-glass, inches:

During the operation of the combustion apparatus, the temperature of the confined space at the aluminum flame is above 3000 C. This temperature maintains the confined area at a very high temperature. The aluminum oxide mist formed from the combustion of the aluminum oxide is in the form of molten droplets of aluminum oxide. These droplets of mist collect on the walls and run down to form a pool of molten aluminum oxide which has a temperature of approximately 2,050 C. The aluminum pool floating on the aluminum oxide is in the molten state and is at a temperature of about 1800 C. Since the temperature of boiling aluminum is 1800 C., the molten aluminum is rapidly vaporizing from the surface 52.

This invention may be employed with a pressure within the apparatus which will increase the temperature of the reaction. The temperature at which the combustion the demand of the rate of burning. This is accomplished reaction may take place with practicality can be further 7 increased by placing the reaction space of the furnace under pressure. The following table shows approximately the expected increase of the vaporization temperature or boiling point of aluminum and aluminum oxide with increase of pressure:

By placing a furnace operating according to this invention under pressure the temperature of vaporization is raised. Raising the temperature of vaporization in turn raises the temperature at which the combustion reaction may be carried on and consequently the heat content differential between the reactants and the products providing in turn greater heat in the reaction space. The limit to the temperature attained by the reaction is the dissociation of the product of combustion. The dissociation in turn is influenced by the total pressure. For example, in burning aluminum, the reaction temperature of 3500 C. at atmospheric pressure can be increased to 4000 C. at ten atmospheres and 4500 C. at 100 atmospheres. It is a feature of the combustion reaction employed in this invention that the temperature of dissociation of the reactant metal is reached in producing the radiant heat energy emission. The radiant heat energy produced is increased with an increase in temperature so that with superatmospheric conditions and higher dissociation temperatures, a higher radiation emission is obtained.

Among the various modifications of the above described embodiments which are within the scope of this invention is a gas tight apparatus to provide a superatmospheric pressure. FIG. 6 illustrates a shutter part for the furnace modified to provide such a gas tight apparatus. In this modification, the shutter is fixed on the top 25 and may be integral therewith. The aperture 39 is retained in the modified shutter and in the upper portion of aperture 39 is fitted and fixed a modified sight glass piece 53. Below the sight glass 53, the aperture 39 is open to the central passage 31 and the combustion reaction. The shutter has a metal shutter disc 54 operable from outside the furnace by a handle 55. The disc 54 is withdrawn into a recess 56, the aperture 39 is open for the emission ofradiation and sight glass 53 is exposed to the combustion reaction. In the other position, the disc 54 is slid in a groove 57 into the lower portion of the aperture 39. In this position, the disc 54 blocks the aperture 39. and screens the sight glass 53 from the combustion reaction. The modified shutter 26 is formed as a solid member with a passage for the disc 54. However, the shutter may be modified to provide a chamber above the passage for circulating water in the manner of the other parts of furnace 23 described above. In this modification shown in FIG. 6, feeding of the metal is accomplished through a stuffing box associated with the feed hole 46 In FIGS. 1, 2, 3 and 7, a preferred embodiment of the combustion apparatus is shown. The combustion apparatus may be made in other forms. One of these forms is shown in HG. 8. Referring specifically to the embodiments shown by the figures, FIG. 8 shows a combustion apparatus 10 according to this invention made up of an. assembly of a spherical pot-furnace 11 and a sight member 12. The spherical furnace 11 is composed of a refractory material such as aluminum oxide and has in one form an inner diameter of about six inches. In

its upper half, the furnace 11 has a sight aperture 13 and a metal feed aperture 14. The sight aperture is about four inches in diameter at the center of the top of the furnace 11. The sight member 12 has a water jacket :15 concentrically surrounding a central passage 16 and has a quartz or Pyrex sight glass window 17 positioned on its upper side over the passage 16. The jacket 15 has a water inlet 18 and a water outlet 19 for passing cooling water through the jacket 15. The jacket 15 is made of plain carbonrsteel and may cemented in place on the furnace 11 with a suitable refractory element. The sight member 12 is also provided with a small /2 inch oxygen inlet 20 extending through the jacket 15 to supply oxygen to the furnace 11. Oxygen passing through inlet 20 flows upward across the sight glass window 17 and then down through the passage 16 into the furnace 11.

The sight member 12 may be provided with a perforated ring attached to the oxygen inlet with perforations opening upward into the central passage 16. After sweeping the window 17, the oxygen provides a downward draft of gas in the passage 16. This downward draft carries any splattering or turbulence away from the window 17. When the supply of oxygen causes the rate of metal combustion to produce a smoke, the draft of oxygen carries the smoke clear of the central passage 16 and maintains a clear passage for the emission of radiation from the furnace 11 through the sight glass 12.

When the combustion apparatus is in operation, the molten pool of aluminum is a large size, and intense radiant energy is emitted through the sight glass over a substantially large area. The intensity of radiation varies over the area of the sight glass. At the full operative intensity, the variation is approximately 14 calories per square centimeter per second at the periphery of the sight glass to approximately 20 calories per square centimeter per second at the center. This provides a very intense radiant energy substantially uniform over a large area.

The combustion apparatus has many advantages in addition to the production of an intense radiant heat. Since the derivation of the heat is dependent upon the release of chemical energy within the furnace, there is no necessity of large power generating apparatus to provide suflicient energy. Therefore, the combustion apparatus is relatively an inexpensive means of producing this heat radiation. In addition to its small size, the equipment is readily portable along with the oxygen tanks required to supply the oxygen for the combustion process. In addition to its portability and low cost, the furnace is rugged in construction and operates without the production of any toxic fumes.

For example, one gram of aluminum generates 7,410 calories in burning. In the performance of the combustion process, aluminum was burned at the rate of 8 to 12 grams per minute in the volume of 2.46 liters. This produced heat over a range from 156,097 calories per minute per liter to 370,337 calories per minute per liter. This rate can be carried higher with faster rates of cooling and also with superatmospheric pressure in the apparatus of this invention. It will also be understood that the reaction of this invention can be conducted at lower rates of heat generation, for example, down to oxidation at a rate of 20,000 calories per minute.

In the above description, the terms radiant energy and radiant heat energy are used interchangeably. It will be understood that the radiation issuing from the combustion reaction and measured by the calorimeter is referred to.

The above described apparatus is an illustrative embodiment of this invention and the radiant energy producing method and apparatus of this invention may be further modified without departing from the spirit thereof. The embodiments and the description are only for the purpose of explanation. It is therefore intended that the invention be limited only by the scope of the appended claims.

This application is a division of abandoned application Serial No. 674,148, filed July 25, 1957, which is a continuation-in-part of my abandoned applications Serial Number 33,346, filed June 16, 1948 and Serial Number 260,424, filed December 7, 1951 and Serial Number 350,856, filed April 24, 1953, and Serial Number 584,811, filed May 14, 1956.

I claim:

1. The method of producing intense radiant heat energy from incandescent area source at a temperature of at least 3000 C. in a furnace having a refractory bottom and a top and sides above said bottom to form a confined chamber with a radiant energy transmitting means in said top for emitting radiant heat energy from said chamber and comprising heating said furnace by burning aluminum and oxygen therein and forming on the refractory bottom a molten aluminum oxide pool with a surface, supplying aluminum to said furnace to form a disc shaped molten pool of aluminum with an upwardly facing flat surface on the surface of said aluminum oxide pool with the aluminum oxide pool providing a molten fluid support having a temperature above the temperature of vaporization of aluminum, transferring heat from the burning of the aluminum to vaporize said aluminum on the upwardly facing surface of the molten pool of aluminum, supplying oxygen to the confined space over the period of the burning in at least stoichiometric proportions above said disc shaped aluminum pool and direoted downwardly to clear a passage through the vaporized aluminum oxide resulting from the prior combustion of aluminum vapors in the confined chamber above the molten aluminum pool and to combine said aluminum vapor above the upwardly facing surface and said oxygen to burn said aluminum in a thin layer over the upwardly facing surface to produce an incandescent area source of radiant heat energy substantially co-extensive with the disc shaped molten aluminum pool and radiating the intense radiant heat energy through the cleared passage above the molten aluminum pool and through the means for emitting radiant heat energy to utilize the intense radiant heat externally of the furnace.

2. The method of producing intense radiant heat energy from an incandescent area source at a temperature of at least 3000 C. having a refractory bottom and walls thereabove to form a confined chamber and comprising forming on the refractory bottom a molten aluminum oxide pool with a surface, supplying aluminum to said furnace to form a disc shaped molten pool of aluminum with an upwardly facing flat surface on the surface of said oxide pool with the aluminum oxide pool providing a molten fluid support having a temperature above the temperature of vaporization of aluminum, transferring heat from said aluminum oxide pool to said molten aluminum pool to vaporize aluminum on the upwardly facing flat surface, supplying oxygen over the period of burning in at least stoichiometric proportions to the confined space and above said disc shaped aluminum pool, directing the oxygen downwardly toward the molten aluminum pool to clear a passage through vaporized aluminum oxide resulting from the combustion of aluminum vapors in the confined chamber above the molten aluminum pool and combining the downwardly directed oxygen with the aluminum vapor to burn the aluminum in a thin layer over the upwardly facing surface to produce an intense radiant heat over an area of the aluminum pool and radiate the intense radiant heat through the cleared passage for heating objects positioned above the molten aluminum pool.

3. A radiant energy producing furnace comprising a casing having an inner wall and an outer wall, said inner wall having a generally concave shape with a refractory bottom for supporting a molten pool of aluminum oxide with a wafer shaped molten pool of aluminum floating thereon, cover means extending over said inner wall to form an enclosed combustion chamber therewith, said outer wall forming a cooling chamber with said inner wall for the circulation of a cooling medium therethrough for cooling said casing, said cover means having a top portion with spaced upper and lower panels forming a second cooling chamber for circulating a cooling medium and having a ring member extending between said upper and said lower panels to form an opening therethrough, and a shutter means movably mounted on said top portion having an opening with heat-resistant transparent means exteriorly adjacent to said ring member and closing said opening and permitting the emission of large quantities of intense radiant energy from the enclosed combustion chamber and having an opaque portion for covering the opening formed by said ring member to block the emission of heat, means for feeding aluminum into said enclosed combustion chamber, passages in said ring member for supplying oxygen to said chamber and having means for directing oxygen supplied therethrough upwardly against said shutter means for cooling said shut ter means and then directed downwardly by reflection from said shutter means into said enclosed combustion chamber to supply a stream of oxygen for clearing a passage through the vaporized aluminum oxide resulting from the combustion of the aluminum vapor below said opening and for burning at a temperature in excess of 3000 C. a layer of vaporous aluminum on the surface of a molten aluminum pool floating on the surface of molten aluminum oxide supported by said refractory bot tom to emit radiant energy over an area through said opening in said cover means.

4. A radiant energy producing furnace comprising a refractory wall having a concave bottom for supporting a molten pool of aluminum oxide with a Wafer shaped molten pool of aluminum floating thereon and having a top forming an enclosed combustion chamber with said bottom for the burning of vaporous aluminum volatilized from said molten aluminum, said top having a ring member forming an opening therethrough, heat resistant transparent means exteriorly adjacent to said ring member and extending across said opening-for closing said opening and permitting the emission of large quantities of intense radiant energy from the enclosed combustion chamber, means in said top for feeding aluminum into said combustion chamber, orifices in said ring member for directing oxygen supplied therethrough upwardly at an angle against said transparent means for cooling said transparent means and then reflected downwardly by the transparent means into the combustion chamber to supply a stream of oxygen for clearing a passage through the vaporized aluminum oxide resulting from the combustion of the aluminum vapor below said transparent means and for burning at a temperature in excess of 3000 C. a layer of vaporous aluminum on the surface of a molten pool of aluminum floating on a pool of molten aluminum oxide to emit radiant energy over an area through said opening and said transparent means.

References Cited in the file of this patent UNITED STATES PATENTS Rasor July 14, 1942 

